Traditional magnetic storage media, such as those employed in disc drives, are essentially uniform and continuous. The density with which data can be written is constrained by the superparamagnetic limit. A solution to overcoming the constraints of the superparamagnetic limit is to organize the magnetic media into a series of individual islands. A benefit of this structure is the increase in a real density that can be achieved over traditional media. However, because the bit islands are discrete, writing data to the disc requires knowledge of the location of each bit island. Therefore, the uniform fabrication of the bit islands is important to providing a high-quality storage medium.
Fabrication of bit-patterned media presents a number of challenges not present in fabrication of conventional media. In particular, there are three factors that define the performance associated with bit-patterned media. The first is reducing the variation between bit islands, such that the sigma or difference associated with the size and shape of each of the bit islands is very low. That is, the bit islands should be uniform in size and shape. The second is reducing the size of each of the bit islands (uniformly) to increase areal density that can be obtained. The third is reducing the pitch (i.e., the distance between adjacent bit islands) to increase the areal density.